Fiber blends



components to thereby provide a stretch fabric.

United States Patent Office Patented fiffflif 3,353,345 FIBER BLENDS Carl John Setzer, Durham, N.C., assignor to Monsanto Company, a corporation of Delaware No Drawing. Filed May 14, 1965, Ser. No. 455,998 7 Claims. (Cl. 57-440) ABSTRACT OF THE DISCLOSURE Stretch fabrics have been manufactured from staple fiber blends of essentially inelastic staple fiber bicomponent fibers wherein the components are derived from polymers the fibers of which are inelastic of spandex polymers. The fiber blend is used to manufacture fabric which may be treated under hot, tensionless conditions to split the bicomponent fiber into its elastic and inelastic This invention relates to essentially inelastic blends of staple fibers. More particularly, the invention relates to essentially inelastic staple fiber blends having an elastic potential which may be developed to provide elasticity at any time during or after the manufacture of fabrics therefrom.

Blends of elastic staple fibers with essentially inelastic staple fibers have been described by Moler in U.S. Patent No. 3,007,227 and Ibrahim in US. Patent No. 3,077,006. Such staple fiber blends are useful in providing a broad array of stretch fabrics which are in turn useful in the manufacture of apparel and the like. The degree of stretch, covering power, hand and other qualities of a fabric may be readily tailored into fabrics manufactured from such blends as indicated in the prior art. These blends are formed by intimately mixing elastic staple fibers, usually prepared from spandex polymers, with -a greater amount of one or more essentially inelastic staple fibers which fibers may be natural or synthetic fibers or, blends of natural and synthetic fibers. Such intimate blends are then processed on conventional textile equipment of the type used to manufacture various knitted, woven and nonwoven fabrics.

Because of the elastic nature of spandex filaments they are difficult to cut to staple length. This problem is recognized in the patent to Ibrahim and a method is therein disclosed whereby certain problems associated with cutting continuous filaments of spandex are overcome by sandwiching layers of tensioned elastic filaments between layers of inelastic filaments and then cutting the several layers of filaments. In this manner the inelastic filaments serve to support the elastic filaments so that the tendency of the elastic filament to contract when out is largely avoided. Elastic staple fibers of uniform length are obtained by cutting in this manner. While the method described by Ibrahim provides a means for obtaining elastic fibers of uniform staple length from continuous elastic filaments, more direct means fOll'gfilCCOl'IlpllShlIlg this end are needed for more economical operation in industrial production of elastic/inelastic staple fiber blends.

Described in the patent to Moler, 'above cited, are methods for blending manufacturing elastic woven, nonwoven and knitted fabrics from staple elastic fibers and natural or synthetic inelastic staple fibers. While Moler indicates that such staple fiber blends may be processed using conventional textile manufacturing equipment to provide stretch fabrics, experience indicates that the stretch and recovery properties of the elastic fiber component of the blends cause serious processing problems particularly when the blend is carded or combed and in conventional Spinning operations. Similarly, it is difiicult to obtain the desired uniformity of product in knitting operations where the elastic yarn has a tendency to stretch unevenly. Such problems are troublesome and invite novel techniques for the manufacture of stretch fabrics from fiber blends comprising highly elastic and inelastic staple fibers.

It is, therefore, an object of this invention to provide novel blends of staple fibers which may be employed in the preparation of stretch fabrics without resort to special processes for cutting continuous elastic filaments.

Another object of this invention is to provide novel blends comprising staple length inelastic fibers which possees an elastic potential reserved for appropriate manufacturing stages so that manufacturing may be accomplished without special considerations necessary where staple fiber based yarns and fabrics which may be made elastic at any desired stage in the manufacturing process. ther objects of this invention will become apparent from the ensuing description.

The objects of this invention are broadly accomplished by providing a blend of different staple fibers wherein at least one component of the blend is non-elastomeric (hereinafter referred to as hard) natural or synthetic fiber or a blend thereof and the other component is an inelastic bicomponent fiber wherein one component of said bicomponent fiber is derived from a hard fiber-forming synthetic polymer and the other component is derived from an elastomeric fiber-forming synthetic polymer, said components of the bicomponent fiber being adhered to one another in a side-by-side relationship along the overall length of the fiber, said bicomponent fiber possessing the property wherein the hard fiber component completely separates or disadheres from the elastomeric fiber component when subjected to heat or hot wet conditions without tension to thereby cause the yarn or fabric to shrink, become bulky and highly elastic. The bulking is caused by contraction of the elastic fiber component upon separation from the hard fiber component.

The staple fiber blend of this invention is normally composed of fibers having a length between 0.75 to about 4.5 inches and deniers of from about 2 to 15.

The bicomponent fiber employed in the blends of this invention are prepared by simultaneously extruding a hard-fiber-forming polymer and elastomeric fiber-forming polymer from the same orifice in a spinnerette to provide a filament, the components of which are adhered at an interface along the length of the fiber, but which com- 3 inelastic and may be very readily cut to staple length for blending by using conventional rotary cutters or other means commonly employed for cutting elastic or hard filaments to uniform staple lengths.

The bicomponent fibers may be prepared in the manner and from materials well known in the art with the general reservation that the polymer candidates for the elastic and hard components of the bicomponent fiber should be selected from those which adhere to one another to the degree that they are separated when subjected to heat or hot wet conditions, rather than by merely stretching. Additionally, the bicomponent staple fibers of this invention may be formed by cutting filaments extruded from dope mixer devices of the type described in copending applications Serial No. 204,707, filed on June 25, 1962 and now abandoned, Serial No. 307,386, filed on Sept. 9, 1963, and now US. Patent No. 3,217,734 and Serial No. 307,449, filed on Sept. 9, 1963.

As previously indicated the blends of this invention are formed from fibers which fall into two categories. They are the hard or inelastic fibers and the bicomponent fibers composed of hard and elastomeric fiber-forming polymers.

The hard or inelastic fibers used in this invention are selected from any class of fibers which may be processed on conventional textile equipment. These fibers are those which undergo elongations of less than about 50- percent before breaking. Among those included within the scope of the invention are the fibers prepared from synthetic fiber-forming polymers, such as polyacrylonitrile, interpolyrners of acrylonitrile with one or more monomers copolymerizable therewith and blends of acrylic polymers; polyamides, such as polyhexamethylene adipamide and polycaproamide; polyesters, such as polyethylene terephthalate; and the like. Natural fibers, such as cotton, wool, silk,- and the like may be employed, as well as fibers such as glass and metal. Of course in the formation of the bicomponent fibers of this invention it is intended that the synthetic polymers be employed. However, bicomponent fibers may be blended according to this invention with any natural or synthetic fiber.

The soft or elastomeric fiber components employed in this invention may be prepared from any elastomeric fiber-forming polymer, the fibers of which have a breaking elongation of greater than about 300 percent, exclusive of elongation related to crimp or coil formation and they are preferably the spandex or segmented polyurethane polymers. The preferred elastomeric fiber components of this invention are those described by H. Rinke, Angewandte Chernie (English ed.) vol. 1, No. 8, pages 419- 424, August 1962, and described more particularly in US. Patents 2,929,804; 2,957,852; 3,097,192 and 3,157,- 619.

The potentially elastic staple fiber blends of this invention normally comprise from about 5 to about 30 percent by weight of spandex polymer. The overall elastomeric fiber content desired when the stretch is developed in the fabric by steam or other means may be provided by taking into account the weight proportion of spandex in the bicomponent fiber and the amount of hard fiber blended with the bicomponent fiber.

EXAMPLE I A 150 filament, 5 denier per filament tow was prepared from a copolymer containing 93.5 percent acrylonitrile and 6.5 percent vinyl acetate by wet spinning in a conventional manner. The tow was reconed with 100 ends being combined to give a tow with a total denier of 75,000. The tow from the combined ends was then fed to a mechanical crimper where 7 crimps per inch were inserted. The crirnped fiber was then fed to a rotary blade staple cutter and the speed of the cutter and tow feed rate were adjusted to cut the tow into staple fiber 2 inches in length.

The staple fibers were then passed through a single process, two-beater type picker to provide a uniform 14 oz. per yarn lap. The lap was then fed to a flat-top card using a long nose (1% inch) feed plate and a feed plate to lickerin setting of 0.022 inch. Flats were set at 0.010 inch and the dofIer roll was set with a clearance of 0.007 inch. The card sliver was passed through three drawing operations, each with six doublings. The sliver obtained from drawing was next drafted into roving using a 1,000 twist multiplier. The roving was converted into 18/1 count yarn with 17F twist per inch using conventional ring spinning and twisting equipment.

A sample of the yarn was exposed to atmospheric steam and did not demonstrate bulking properties. Another sample of the yarn was knitted into 4-inch knit tubing and the tubing exposed to boiling water. The tubing properties did not change significantly after exposure to boiling water.

EXAMPLE II A bicomponent fiber was prepared from equal volumes of 25 percent total solid dopes where one dope containing a polymer of 93.5 percent acrylonitrile and 6 .5 percent vinyl acetate and the other dope contained a polyurethane elastomeric polymer prepared from a glycol terminated polyester capped with m-phenylene diisocyanate and extended with hydrazine. The viscosity of the latter dope was 11,500 cp., at 25 C. The equal volumes of dopes were fed to a plate mixer device of the type described in copending Serial No. 307,386 and wet spun by extrusion from 150, 5 mil. holes in a spinnerette into a bath of dimethylacetamide and water (40/60) at about 35 C. and then given a water wash and a 4.5 X strength to form an inelastic 6 d.p.f. bicomponent fiber. The bicomponent fiber was combined as described in Example I, crimped and cut into 2-inch staple length fiber.

This bicomponent staple fiber was blended by feeder blending with the staple fiber described in Example I in a ratio of 3 parts of the bicomponent staple to 7 parts of the staple fiber from Example I. The blend of staple fibers was processed through the same system described in Example I. No processing difficulties were encountered. In no case was any of the conventional textile equipment employed in the manufacture described in Example I altered in any way to facilitate the processing of the blend.

A portion of the yarn prepared from the blended fibers was then exposed in a tensionless state to steam at atmospheric pressure for approximately 10 seconds whereupon the yarn developed highly crimped, bulky, elastic structure. The yarn shrinkage was approximately 50 percent.

The yarn prepared in this example was knitted. The knitted product was exposed to boiling water without tension and immediately formed a bulky fabric which possessed significantly improved covering capacity, elasticity and an improved hand. A microscopic examination of the fibers taken from the fabric revealed that the bicomponent portion of the fiber had separated after exposure to hot humid condition into separate and distinct fiber components.

It will be recognized by those skilled in the art that the process and products of this invention provide a means for readily incorporating stretch properties into fabrics without difficulty on conventional apparatus.

I claim:

1. An essentially inelastic staple fiber blend comprising,

(a) hard staple fibers which are essentially inelastic and (b) bicomponent staple fibers composed of at least one hard inelastic fiber component and at least one elastomeric fiber component, said elastomeric and hard fiber components being adhered to one another in a side-by-side relationship throughout the length of the fiber, said bicomponent fiber being essentially inelastic and having the property whereby the elastomeric and hard components separate when subjected to hot tensionless conditions.

2. An essentially inelastic yarn comprising the staple fiber blend of claim 1.

3. A fabric comprising the staple fiber blend of claim 1.

4. The blend of claim 1 wherein said hard staple fibers comprise polymers containing at least 85 percent by Weight of acrylonitrile.

5. The blend of claim 1 wherein said hard inelastic component comprises a polymer containing at least 85 percent by weight of acrylonitrile.

6. The blend of claim 1 wherein said elastomeric fiber component comprises a segmented polyurethane polymer.

7. In a process for the manufacture of stretch fabrics containing staple fibers of a synthetic elastomeric polymer, the improvement which comprises blending hard staple fibers with inelastic bicomponent fibers wherein the components of bicomponent fibers are drived from hard fiber- 6 and subjecting the inelastic fabric so prepared to hot, tensionless conditions whereby the fabric shrinks and becomes elastic as a result of separation of components of said bicomponent fibers.

References Cited UNITED STATES PATENTS 3,007,227 11/ 1961 Moler 57-140 3,077,006 2/1963 Ibrahim 19-148 3,117,906 1/1964 Tanner 16v1--177 3,244,785 4/ 1966 Hollandsworth 264171 FRANK J. COHEN, Primary Examiner.

forming polymers and elastomeric fiber-forming polymers 15 JOHN AK xamin r. 

1. AN ESSENTIALLY INELASTIC STAPLE FIBER BLEND COMPRISING, (A) HARD STAPLE FIBERS WHICH ARE ESSENTIALLY INELASTIC AND (B) BICOMPONENT STAPLE FIBERS COMPOSED OF AT LEAST ONE HARD INELASTIC FIBER COMPONENT AND AT LEAST ONE ELASTOMERIC FIBER COMPONENT, SAID ELASTOMERIC AND HARD FIBER COMPONENTS BEING ADHERED TO ONE ANOTHER IN A SIDE-BY-SIDE RELATIONSHIP THROUGHOUT THE LENGTH OF THE FIBER, SAID BICOMPONENT FIBER BEING ESSENTIALLY INELASTIC AND HAVING THE PROPERTY WHEREBY THE ELASTOMERIC AND HARD COMPONENTS SEPARATE WHEN SUBJECTED TO HOT TENSIONLESS CONDITIONS. 